Aerosol for viscous products

ABSTRACT

An aerosol dispensing container  1  comprising a container body  20, 30, 40  and a collapsible bag  50  therein. The bag  50  separates a pressurised chamber defined between the container body  20, 30, 40  and the bag  50  from a product chamber defined inside the bag  50.  A valve  5  is mounted in a valve cup  70  supported by the body  20, 30, 40  and the valve arrangement allows fluid communication between the valve  5  and the product chamber inside the bag  50.  An extrinsic support means  54, 55  is carried by the bag  50  and is adapted to ensure flow of product to the valve  5  by preventing radial collapse of the bag  50,  whilst allowing axial collapse of the bag  50  as the product is dispensed.

TECHNICAL FIELD

The present invention relates to aerosol containers comprising an outer casing with a bag for product encapsulated therein. Such containers are commonly referred to in the art as bag-in-can aerosols.

In particular, the invention relates to adaptation of such bag-in-can systems to allow expulsion of viscous products, for example in the form of pastes or thick gels. Such products may include adhesives, sealants and fillers.

BACKGROUND ART

Bag-in can aerosol dispensers have been known from the prior art since the 1960′s. For example, GB 1030596 (ALLIED CHEM) May 22, 1966 describes the manufacturing method used for production of a nylon bag and its incorporation into such an aerosol container.

In later years, such systems were enhanced to provide various improvements to the bag structure and dispensing characteristics. For example, U.S. Pat. No. 3,539,083 (DART IND INC) Nov. 10, 1970 describes modification of the bag and can structure to ensure that the bag cavity fills the can and also the incorporation of a dip tube inside the bag to ensure that when the valve is opened, product being dispensed from the container does not itself throttle further product dispensing. U.S. Pat. No. 4,148,416 (METAL BOX CO LTD) Oct. 4, 1979 describes a loose core member within the bag, which prevents the formation of “pockets” within the product as the bag collapses and product is dispensed.

Whilst the disclosure in the prior art is suitable for many products, such aerosols are now being proposed for more challenging, viscous products. The viscosity of the products now being considered for such bag-in-can technology exacerbates the problems of throttling the product flow from the aerosol valve and the uneven or even lack of dispensing of some product from the container.

Where a product is very thick the bag-in-can system will tend to dispense the product nearest the valve adequately. However, as product is dispensed the bag tends to collapse near the valve, sealing the path between the remaining product and the valve. Thus, it becomes very difficult or impossible to expel some of the product, which remains trapped within the aerosol container. The viscosity of the product means that the use of a dip tub is impractical and a free-floating core will not provide a flow path necessary to dispense the product.

Historically, bags with pleats or folds created using only the material of the bag sidewall, “pleated bags”, have been a popular way of trying to control the collapsing of the product bag. The bags are typically made from a plastics material and are shaped using conventional blow-moulding techniques to introduce folds or pleats in the bag sidewall. These folds or pleats are usually ‘V’ or ‘U’-shaped in transverse cross-section and generally have a decreasing sidewall thickness as the diameter of the bag increases from its pre-shaped form due to stretching of the material. Their effect is to introduce an annular or circumferential weakening or bands in the bag, which permits the bag to collapse under applied forces. U.S. Pat. No. 3,471,059 A (J. L. MOLLER ET AL) Oct. 7, 1969 describes a dispensing container with such a pleated bag. The bag is formed from an integral piece of material and includes axially spaced primary fold sections and secondary fold bands collapsible subsequent to the collapse of the primary fold sections. The intention of the paneling is to regulate the collapse of the bag caused by the pressure forces acting on it radially and axially as product is dispensed. U.S. Pat. No. 4,062,475 A (HARRIS AND MONSON) Dec. 13, 1977 also describes in one particular embodiment a bag (flexible liner, 9) with horizontally pleated sides. Again, the Figures of U.S. Pat. No. 4,056,213 A (MARTIN PAINT) Nov. 1, 1977 show a pleated bag with the pleats or folds forming a collapsible bellows or piston. In GB 1116423 A (CONTINENTAL CAN) Feb. 28, 1967 such folds are used both to rigidify the bag (circumferentially extending first means, 25) and to regulate the collapse of the bag (circumferentially extending second means, 26). In practice however a pleated collapsible bag does not work very well; the inventor has found that pleated bags are prone to collapsing inwardly radially despite the teachings of Moller, Harris, Martin Paint and Continental Can. The decreasing bag sidewall thickness of the pleats or folds is insufficient, especially in combination with highly viscous products, to withstand the pressure of the propellants used these days and pleated bags still tend to collapse uncontrollably resulting in undispensed product. There remains the need to provide a strong product bag which will collapse predictably under the applied influence of propellant and the inventor has found that only extrinsic support means, i.e. those added to the bag, as opposed to intrinsic support means which are made out of the bag material such as folds or pleats, will suffice.

DISCLOSURE OF INVENTION

Accordingly, the present invention provides an aerosol dispensing container comprising a container body and a collapsible bag therein to separate a pressurised chamber defined between the container body and the bag from a product chamber defined by the bag, and an actuating valve carried by the container body and arranged in fluid communication with the product chamber, characterised in that the bag includes extrinsic support means adapted to prevent radial collapse of the bag to maintain flow of product to the valve whilst allowing axial collapse of the bag as the product is dispensed.

As product is dispensed from the aerosol container, the bag tends to collapse radially, but the support means keeps the walls of the bag at a defined distance, preventing further radial collapse and defining a flow path for the remaining product to the aerosol valve.

The inventor has used both a cage-like structure and subsequently a conventional spring as the support means with similar results. The cage or spring is preferably located inside the bag and it is therefore submerged in the product. Therefore, the material from which the cage or spring is made must be chosen carefully. The cage or spring must not be adversely affected by the product (e.g. it must not corrode) and neither must it adversely affect the product (e.g. by chemical reaction). The cage or spring should also be arranged so that it does not inhibit or prevent the flow of product to the actuating valve.

BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS

Different embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 shows a cut away isometric drawing of a prior art aerosol container with bag and an expanded area of the top section of this container.

FIG. 2 shows a cross section view through an aerosol container according to the invention with a helical spring located inside the bag.

FIG. 3 shows a cross section through the same aerosol container as that shown in FIG. 2, after the contents of the bag has been dispensed and the helical spring is compressed.

FIG. 4 shows a cross section view through an aerosol container according to a second embodiment of the invention where ribs are situated within the product compartment and are adapted to define a bellows structure, which prevents radial collapse of the bag, whilst allowing axial compression of the bag.

FIG. 5 shows a cross section view through an aerosol container according to another embodiment of the invention, in which the bag sidewall incorporates ribs designed to prevent radial collapse of the bag, whilst allowing axial compression of the bag.

Referring to FIG. 1, a prior art aerosol container 1 comprises a body 30 having a base 20 and a cone 40. The free edge of the cone 40 is finished with a curl 42. The base 20 and cone 40 are connected to the body 30 using conventional joining methods, such as a double seam. The base 20 defines a charging port or aperture 25, through which propellant is inserted into the aerosol container 1, the propellant being used to drive any product in the aerosol container 1 out of the valve 5, when it is opened. The propellant may either take the form of a liquidified propellant or a compressed gas.

The aerosol container 1 shown in FIG. 1 is a conventional “bag in can” aerosol. A bag 50 is inserted into the body 30. The inside of the bag 50 defines a product compartment and the space left outside the bag 50, between the bag 50 and the body 30, defines a propellant compartment into which propellant is introduced via the charging port 25. Once propellant has been inserted into the propellant compartment, the charging port 25 is sealed with a grommet 26.

FIG. 2 illustrates a first embodiment of the invention, in which a spring 54 is inserted into the neck 57 of the bag 50 in the vicinity of the valve 5. The valve 5 is mounted in a valve cup 70 and is arranged in fluid communication with the product compartment inside the bag 50. The spring 54 is arranged to brace the sidewall 53 of the bag against radial collapse, whilst allowing the base 52 of the bag to collapse axially.

FIG. 3 illustrates the same embodiment of the invention as FIG. 2, but this figure shows the spring 54 in its compressed configuration. As product is forced out of the valve 5, by the propellant acting on the bag 50, the spring 54 braces the bag 50 and prevents radial collapse. This ensures that the flow path of product to the valve 5 is maintained. As product is used up the spring 54 compresses axially, ensuring that most of the product is dispensed from the bag 50 through the valve 5.

A disadvantage of this arrangement is that the spring 54 is submerged in the product inside the bag 50. This may cause the spring 54 to become “clogged” by the product, thus restricting its effective operation. In order to overcome this problem, the spring 54 may need to be made of more expensive materials (such as stainless steel), which is uneconomic for many aerosol applications. Spring materials that are inert in the presence of a wide variety of products are prohibitively expensive, often costing many times the cost of the finished aerosol product on the supermarket shelf.

To avoid “clogging” of the spring, the inventor has designed an alternative bag arrangement (as shown in FIG. 4), in which ribs 55 are provided around the circumference of the bag 50 in fluid communication with the product compartment, the sidewall 53 in between the ribs 55 acting as a flexible web. The ribs 55 and the flexible sidewall 53 therebetween form a bellows structure. The ribs 55 are adapted to prevent radial collapse of the bag 50 whilst the bellows structure allows axial compression of the bag 50. The ribs 55 can be of any cross-section, for example, hexagonal, but preferably they have a circular cross-section. A disadvantage of this bellows structure is that it is difficult to manufacture and makes assembly of the bag 50 inside the aerosol body 30 complex.

FIG. 5 shows a third embodiment of the invention, which requires no spring or like component inside the bag 50 and no ribs 55, which are difficult to assemble inside the aerosol body 30. In this embodiment of the invention, one or more ribs 55 are provided integrally with the sidewall 53 of the bag 50. The ribs 55 may be arranged to form a helix or may be provided as segments of a helix, i.e. they may be continuous or discontinuous. The ribs 55 are designed and arranged to restrict radial collapse of the bag 50, whilst allowing axial compression of the bag 50 in much the same way as the spring 54 (shown in FIGS. 2 and 3) and the ribs 55 shown in FIG. 4. 

1. An aerosol container for dispensing a product, comprising: a container body, a collapsible bag disposed therein in the container body, a pressurized chamber defined between the container body and the bag, a product chamber defined inside the bag, a valve carried in a valve cup, the valve arranged in fluid communication with the product chamber, the bag including extrinsic support structure adapted to prevent radial collapse of the bag to maintain the flow of product to the valve, whilst while allowing axial collapse of the bag as the product is dispensed.
 2. An aerosol container according to claim 1, wherein the support structure means comprises a cage or spring.
 3. An aerosol container according to claim 2, wherein the spring is disposed within the bag.
 4. An aerosol container according to claim 1, wherein the support structure comprises one or more circumferential or helical ribs carried by the bag.
 5. An aerosol container according to claim 4, wherein the ribs are carried on the outside of the bag.
 6. An aerosol container according to claim 4, wherein the ribs are located within the wall thickness of the bag.
 7. An aerosol container according to claim 4, wherein the ribs are discontinuous.
 8. An aerosol container according to claim 4, wherein the ribs and the intervening sidewall of the bag are arranged to define a bellows structure.
 9. An aerosol container according claim 1 wherein the support structure means is made from a material that is compatible with the product.
 10. An aerosol container according claim 1, wherein the support structure is a cage.
 11. An aerosol container according claim 10, wherein the cage is disposed within the bag. 